TAILIEUCHUNG - An Encyclopedia of the History of Technology part 20

An Encyclopedia of the History of Technology part 20. This one of a kind encyclopedia presents the entire field of technology from rudimentary agricultural tools to communication satellites in this first of its kind reference source. Following an introduction that discusses basic tools, devices, and mechanisms, the chapters are grouped into five parts that provide detailed information on materials, power and engineering, transportation, communication and calculation, and technology and society, revealing how different technologies have together evolved to produce enormous changes in the course of history | PART ONE MATERIALS making steel in France by Emil and Pierre Martin in 1863. Siemens set up a small works in Birmingham in 1866 to demonstrate how steel could be made in his furnace and by 1869 a company at Swansea was producing about 75 tonnes a week. By 1870 the Siemens process often called the Siemens-Martin process for the obvious reason was fully established. Wrought iron now had some really serious competition. The Siemens and Bessemer processes were complementary but both could use phosphoric or non-phosphoric iron. Bessemer was cheaper since it used no fuel but it needed to be charged with molten iron. This was easy when the Bessemer plant was adjacent to blast furnaces. Molten iron could be used in the Siemens openhearth furnace and it often was but an advantage of this process was that it could melt scrap iron. With the spread of industry scrap had become a useful raw material as machinery of all kinds wore out or was replaced by new and better types and it was cheaper than pig iron. See Figure . The Siemens process was slower than the Bessemer. A Bessemer charge of iron took about thirty minutes to convert to steel in the Siemens furnace it took eight to twelve hours. This could be an advantage for it enabled the furnace operator to make frequent checks on the steel and to adjust its composition as required. Various grades were now demanded and the new steelmaking processes were able to provide them. In the second half of the nineteenth century steel began slowly but surely to push the wrought iron trade out of existence although it survived in a small way until recently from about 1870 onwards steel was what really mattered. Cast iron continued to be made partly for castings but increasingly as the raw material for steel and this is still the position today. Alloy steels Before 1856 there were only two important iron products cast and wrought iron. A third carbon steel was essential for some purposes but its output was small. Bessemer added a fourth

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